How Do Liquid-Junction Potentials and Medium Polarity at Electrode Surfaces Affect Electrochemical Analyses for Charge-Transfer Systems?

The importance of electrochemical analysis for charge-transfer science cannot be overstated. Interfaces in electrochemical cells present certain challenges in the interpretation and the utility of the analysis. This publication focuses on: (1) the medium polarity that redox species experience at the electrode surfaces that is smaller than the polarity in the bulk media and (2) the liquid-junction potentials from interfacing electrolyte solutions of different organic solvents, namely, dichloromethane, benzonitrile, and acetonitrile. Electron-donor-acceptor pairs of aromatics with similar structures (i.e., 1-naphthylamine and 1-nitronaphthalene, 10-methylphenothiazine and 9-nitroanthracene, and 1-aminopyrene and 1-nitropyrene) serve as redox analytes for this study. Using the difference between the reduction potentials of the oxidized donors and the acceptors eliminates the effects of the liquid junctions on the analysis of charge-transfer thermodynamics. This analysis also offers a means for evaluating the medium polarity that the redox species experience at the surface of the working electrode and the effects of the liquid junctions on the measured reduction potentials. While the liquid-junction potentials between the dichloromethane and acetonitrile solutions amount to about 90 mV, for the benzonitrile-acetonitrile junctions, the potentials are only about 30 mV. The presented methods for analyzing the measured electrochemical characteristics of donors and acceptors illustrate a means for improved evaluation of the thermodynamics of charge-transfer systems.

Liver Metastasis Modulate Responses of Suppressive Macrophages and Exhausted T Cells to Immunotherapy Revealed by Single Cell Sequencing

Liver metastasis is associated with immunotherapy resistance, although the underlying mechanisms remain incompletely understood. By applying single cell RNA-sequencing to a concurrent subcutaneous and liver tumor murine model to recapitulate liver metastases, it is identified that subsets within tumor-infiltrating exhausted CD8⁺ T (Tex) cells and immunosuppressive tumor-associated macrophages (TAMs) display opposite responses to concurrent liver tumors and anti-PD-1 treatment, suggesting a complex immune regulating network. Both angiogenic and interferon-reactive TAMs show increased frequencies in implanted liver tumors, and anti-PD-1 treatment further elevates the frequencies of angiogenic TAMs. Such TAMs frequencies negatively correlate with the proportions of cytotoxic T cell subsets. Further, expression of interferon-stimulated genes in TAMs is dramatically reduced under effective anti-PD-1 treatment, while such tendencies are diminished in mice with implanted liver tumors. Therefore, the study indicates that liver metastases could increase immunosuppressive TAMs frequencies and inhibit Tex responses to PD-1 blockade, resulting in compromised systemic antitumor immunity and limited immunotherapy efficacy.

Individual lifetime benefit from low-dose colchicine in chronic coronary artery disease patients

Background

Low-dose colchicine reduces the risk of cardiovascular events in patients with chronic coronary artery disease (CAD), but the absolute benefit may vary between patients. Individual benefit from preventive therapies can be estimated using the guideline-recommended SMART-REACH model.

Purpose

This study aimed to assess the range of individual absolute 10-year and lifetime benefit from low-dose colchicine according to patient risk profile.

Methods

The SMART-REACH model was combined with the relative treatment effect of low-dose colchicine, and applied to all participants from the LoDoCo2 trial (n=5,522), and patients with chronic CAD from the UCC-SMART cohort (n=5,308). Individual treatment benefit was expressed as (i) 10-year absolute risk reductions (ARRs) for myocardial infarction, ischemic stroke, or cardiovascular death (MACE), and (ii) life-years gained free of MACE. Predictions were also performed for MACE plus ischemia-driven coronary revascularization (MACE+), through development of a new competing risk-adjusted lifetime prediction model in data from the REACH registry (n=14,522). Low-dose colchicine was compared to alternative intensive prevention goals, i.e. low density lipoprotein-cholesterol (LDL-c) reduction to <1.4 mmol/L, and systolic blood pressure (SBP) reduction to <130 mmHg.

Results

Median individual 10-year ARR for MACE from low-dose colchicine therapy was 4.6% (interquartile range [IQR] 3.6–6.0%), and median gain in life expectancy free of MACE was 2.0 (IQR 1.6–2.5) years. Median 10-year ARR for MACE+ was 8.6% (IQR 7.6–9.8%), and median gain in MACE+-free life expectancy was 3.4 (IQR 2.6–4.2) years. For intensified LDL-c and SBP reduction respectively, median 10-year ARRs were 3.0% (IQR 1.5–5.1%) and 1.7% (IQR 0.0–5.7%) for MACE, and 5.2% (IQR 2.5–8.7%) and 2.9% (IQR 0.0–9.5%) for MACE+. Median life-years gained from LDL-c and SBP reduction were 1.2 (IQR 0.6–2.1) and 0.7 (IQR 0.0–2.3) years free of MACE, and 1.8 (IQR 0.8–3.3) and 0.9 (IQR 0.0–3.4) years free of MACE+.

Conclusion

The individual absolute benefit from low-dose colchicine varies between patients. In an era where lipid- and blood pressure-lowering therapies are already routinely used, the benefits of low-dose colchicine are expected to be of at least similar magnitude to those of intensified LDL-c and SBP reduction in patients with chronic CAD.

Funding Acknowledgement

Type of funding sources: None.

Sex-based differences of the impact of aortic valve calcium score on mortality and post-procedural outcomes after trans-catheter aortic valve replacement

Introduction

Sex based differences exist in the presentation, outcomes, and management of cardiovascular diseases. Although aortic valve calcium (AVC) score has been postulated to be associated with post-procedural outcomes after transcatheter aortic valve replacement (TAVR), data on the impact of AVC score on procedural outcomes after TAVR based on sex have been scarce.

Objective

The aim of the present study was to elucidate sex related differences in the prognostic impact of AVC score as a predictor of post-procedural outcomes and mortality in patients with severe aortic stenosis (AS) who underwent TAVR.

Methods

We retrospectively abstracted the records of 497 patients with severe AS who underwent TAVR between January 2016 and July 2019 at our institution. All patients underwent a non-contrast cardiac CT scan on a Siemens Somatom Definition Flash 128 slice scanner. AVC score using the Agatston method was calculated retrospectively. Primary outcome was 1-year mortality. Patients were divided into two groups: 1) Non-severe AVC score group [women <1200 Agatston unit (AU) and men <2000 AU]; 2) Severe AVC Score group [women >1200 AU and men >2000 AU]. Cox-regression model was used to predict effect of variables on 1-year mortality in male and female patients.

Results

Among 466 patients included, 268 patients were male and 198 were female (57.5% vs 42.5%). When compared with males, female patients had significantly lower AVC score (p<0.001), aortic valve area (AVA) (p<0.001), obstructive CAD (p<0.001), and history of previous PCI (p<0.004), and CABG (<0.001) but had a significantly higher STS score (6.7±3.2 vs 5.8±3.3 P=0.01). There was no difference between need for permanent pacemaker (PPM) implantation (11% vs 9.6%, p=0.4), major complications (16% vs 15%, p=0.9), stroke (0.8% vs 1.6%, p=0.7), 30-day (3.7% vs 4%, p=0.9), and 1-year mortality (14% vs 12%, p=0.6) between males and females, respectively. Female patients required smaller bio-prosthetic valves compared with males (26±3.2 vs 30±3, p<0.001). Cox regression analysis for female patients showed BMI, hemoglobin level, and AVA independently predicted 1-year mortality, while there was no impact of severe AVC score (>1200 AU) on 1-year mortality in females. Similarly, Cox regression analysis for male patients showed there was no impact of severe AVC score (>2000 AU) on 1-year mortality in males. When males in the severe AVC group were compared with female patients in the severe AVC group, there was no difference in 30 day (4.3% vs 3.3%, p=0.82) and 1-year mortality (14.2% vs 13.3%, p=0.77). Similarly, in the severe AVC group there was no difference between need for PPM implantation (12.8% vs 12.1%, p=0.9), major complications (19.7% vs 15.8%, p=0.4), and stroke (2.2% vs 1%, p=0.6) between males and females, respectively.

Conclusion

There were no sex differences in the impact of AVC score on mortality and post-procedural outcomes after TAVR.

Funding Acknowledgement

Type of funding sources: None.

Comparing direct oral anticoagulants versus vitamin K antagonist in patients with atrial fibrillation after transcatheter aortic valve replacement: an updated meta-analysis

Background

Oral anticoagulation therapy is indicated for patients undergoing transcatheter aortic valve replacement (TAVR) with concomitant or new onset atrial fibrillation (AF). However the data on optimal anticoagulation regimen in this population remains unclear.

Purpose

To compare efficacy and safety outcomes of direct oral anticoagulants (DOACs) versus Vitamin K antagonists (VKA) in patients with AF post TAVR.

Methods

We searched electronic databases (PubMed, Embase, Scopus, Cochrane) from inception to February28th, 2022 using MeSH terms and keywords for DOACs, AF or TAVR. Primary outcome of interest was all-cause stroke or systemic embolic event. Secondary safety outcomes were major bleeding and all-cause mortality. Pooled risk ratio (RR) and 95% confidence interval (CI) were calculated using a random-effects model. Interstudy heterogeneity was assessed using the Higgins I 2 value. All statistical analysis were performed using RevMan 5.4.1 software.

Results

We identified five eligible studies (1RCT, 4 observational) including 3694 patients (DOAC n=1581, VKA n=2113). The mean age was 81.4±0.9 years. The mean follow-up was 12.4±14.3 months. Type of DOACs included apixaban (n=394, 24.9%), rivaroxaban (n=354, 22.4%), dabigatran (n=119, 7.5%) and edoxaban (n=714, 45.2%).There was no significant difference in primary outcome of stroke or systemic embolic event (RR: 0.93; CI: 0.65–1.33; p>0.05; I2=5%), or in secondary outcomes of major bleeding (RR: 1.02; CI: 0.78–1.34; p>0.05; I2=44%) and all-cause mortality (RR: 0.87; CI: 0.59–1.27; p>0.05; I2=56%) between DOACs and VKA groups.

Conclusion

This meta-analysis shows anticoagulation therapy with DOACs has similar safety and efficacy outcomes compared to VKA in patients with AF undergoing TAVR.

Funding Acknowledgement

Type of funding sources: None.

Bentracimab demonstrates reversal of antiplatelet effects of ticagrelor: impact of hematocrit and generic versions of ticagrelor in vitro

 

Recent clinical studies demonstrated bentracimab provides immediate and sustained reversal of ticagrelor's antiplatelet effects in patients undergoing surgical procedures or with bleeding. Ticagrelor reversal was assessed by VerifyNow PRUTest (VN) and other platelet function testing assays in Phase I-III studies. As decreases in hematocrit (hct) may impact the VN result, it remains to be demonstrated whether this assay can detect platelet function restoration by bentracimab in bleeding patients with low hct. Additionally, bentracimab utility against generic ticagrelors is unknown. The purpose of this study was to determine the impact of decreased hct and generic forms of ticagrelor on platelet function and subsequent reversal by bentracimab, as measured by light transmission aggregometry (LTA) and VN. The hct level in blood samples collected from healthy volunteers (n=10) was sequentially lowered to 32, 30, 25, 22.5, 20 or 15% by addition of autologous platelet-rich plasma to whole blood with matching platelet counts. Prepared samples were treated with nothing, vehicle, or ticagrelor (3.0 μg/mL) followed by treatment with bentracimab (1.2 mg/mL). In a separate study, blood collected from healthy volunteers (n=10) was treated with nothing, vehicle, ticagrelor or generic ticagrelors (3.0 and 5.6 μg/mL; mean and peak plasma levels in the Phase 1 trial) prior to addition of bentracimab (0, 0.6, 1.2, 1.8 and 2.4 mg/mL; below the reported minimum to peak plasma level) to demonstrate a dose response. Reversal was assessed by either ADP-mediated LTA or VN or both assays. Results show a decrease in hct to <30% significantly increased the PRU in untreated samples (p<0.05). Ticagrelor treatment significantly decreased the PRU in all hct groups (p<0.0001). When normalized to each donor's baseline PRU values, bentracimab reversed the ticagrelor effects within 10-min, restoring the PRU value to 54–73% for all hct groups. PRU values were further restored to 85–93% of baseline PRU after 1-hr treatment. The PRU inhibition for both 10-min and 1-hr treatments were not significantly different across the hct groups, except for the 10-min treatment in the 15% hct group vs. unadjusted hct group (p<0.05), suggesting equivalent reversal by bentracimab across the hct range. In the second study, treatment with generic ticagrelor demonstrated significant platelet inhibition and was comparable to standard ticagrelor. Bentracimab (>0.6 mg/mL) immediately restored platelet function after ticagrelor treatment to 80–100% of baseline using the VN test. LTA data demonstrated similar results to VN, but as expected, reversal was less robust with 5.6 μg/mL ticagrelor + 0.6 mg/mL bentracimab combination (mean 55% of baseline values). Collectively, these data suggest the VN test can effectively measure the antiplatelet effects of ticagrelor and subsequent reversal, even at low hct, and bentracimab is also capable of reversing the antiplatelet effects of generic forms of ticagrelor.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): PhaseBio Pharmaceuticals, Inc

Lipoprotein(a), cardiovascular events, and benefit of P2Y12 inhibition: insights from the PEGASUS-TIMI 54 trial

Background

Lp(a) plays a causal role in atherogenesis and may exert pro-thrombotic effects by inhibiting fibrinolysis owing to its structural homology with plasminogen. Patients with higher Lp(a) concentrations may derive greater benefit from anti-thrombotic therapy.

Purpose

We assessed whether patients with higher Lp(a) derive greater risk reduction from P2Y12 inhibition with ticagrelor vs. placebo on a background of aspirin therapy.

Methods

Lp(a) concentration was measured (Randox) in a prospective nested cohort of 8,967 pts enrolled in PEGASUS-TIMI 54, a randomized trial of ticagrelor vs. placebo in patients 1–3 years post MI (median follow-up: 2.7 y). Lp(a) was dichotomized at 200 nmol/L as an established threshold of risk. The prespecified MACE endpoint was CV death, MI or stroke, with KM rates reported at 3y. Cox proportional hazards were used to assess the relationship between Lp(a), MACE and treatment benefit. Models were adjusted for relevant baseline characteristics including apolipoprotein B.

Results

The median Lp(a) was 29 (25th-75th percentile: 12–137) nmol/L. A total of 1,053 pts (11.7%) had a high Lp(a) (≥200 nmol/L). In the pooled trial population, high Lp(a) concentration was associated with a 29% higher risk of MACE (9.1% vs 7.6%; adjusted hazard ratio [adj HR] 1.29, 95% confidence interval [CI] 1.02–1.62; p=0.03), including a 37% higher risk of MI (6.9% vs. 5.3%; adj HR 1.37, 95% CI 1.05–1.79; p=0.02). The hazard ratios for MACE with ticagrelor vs. placebo were 0.73 (95% CI 0.48–1.11) for patients with higher Lp(a) and 0.88 (95% CI 0.74–1.05) for patients with lower Lp(a) (p-interaction=0.41; Figure 1). The absolute risk reductions were 2.4% and 1.2%, respectively.

Conclusion

Lp(a) above 200 nmol/L identifies patients with prior MI at increased risk of MACE who may derive greater absolute risk reduction from treatment with ticagrelor. These exploratory observations provide insights for therapeutics that are evaluating the clinical benefit of Lp(a) reduction.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The PEGASUS-TIMI 54 trial was funded by AstraZeneca

To compare efficacy and safety of direct oral anticoagulants in patients with concurrent atrial fibrillation and bioprosthetic heart valve repair or replacement: a systematic review and meta-analysis

Background

Use of direct oral anticoagulants (DOACs) is contraindicated in patients with mechanical valves. However data on their use in patients with atrial fibrillation (AF) and bioprosthetic valves (BV) is still limited.

Purpose

To assess the safety and efficacy of DOACs versus Vitamin K antagonist (VKA) in patients with AF after BV repair or replacement.

Methods

We performed a comprehensive review of electronic databases (PubMed, Embase, Scopus, Cochrane) using MeSH terms and keywords for DOACs, AF and BVs from inception through December 2021. Randomized clinical trials (RCT) or observational studies that reported clinical outcomes comparing DOACs versus VKA in patients with AF and BVs were eligible for inclusion. Ten articles were reviewed for full text. Primary outcome was a composite of all cause stroke or systemic embolic event.

Secondary outcomes included major bleeding and all-cause mortality. Subgroup analysis stratified by study design was performed. Pooled risk ratio (RR) and 95% confidence interval (CI) were calculated using Mantel-Haenszel method with DerSimonian-Laird estimator for tau2 for random effects model.

Interstudy heterogeneity was assessed using the Higgins I 2 value. All statistical analysis was performed using RevMan 5.4.1 software.

Results

Ten studies (5 RCTs, 5 observational studies) with a total of 5,333 patients (DOACs n=2434; VKA n=2899) were included. Aortic, mitral and mixed BV repair or replacement were 74.2%, 25.6% and 0.02% respectively. The mean age was 72.6±11.9 years. The mean follow-up was 15.7±12.9 months. Type of DOACs included apixaban (n=553, 22.7%), rivaroxaban (n=893, 36.7%), dabigatran (n=151, 6.2%) and edoxaban (n=837, 34.4%). There was no significant difference in primary outcome of stroke or systemic embolic event (RR: 0.79; CI: 0.56–1.11; p>0.05; I2=12%) or secondary outcomes of major bleeding (RR: 0.84; CI: 0.64–1.11; p>0.05; I2=45%), and all-cause mortality (RR: 0.84; CI: 0.64–1.11; p>0.05; I2=29%) between DOACs compared with VKA.

Conclusion

In patients with AF and BV, DOACs are non-inferior to VKA for risk of stroke or systemic embolism, major bleeding, and all-cause mortality. Thus, DOACs can serve as a viable alternative to VKAs which have a narrow therapeutic index, multiple drug interactions, and require frequent monitoring.

Funding Acknowledgement

Type of funding sources: None.

Cardiovascular benefits outweigh risks in patients with atrial fibrillation in REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial)

Background/Introduction

REDUCE-IT, a multinational, double-blind trial, randomized 8179 statin-treated patients with controlled low density lipoprotein cholesterol, elevated triglycerides, and cardiovascular (CV) risk, to icosapent ethyl (IPE) 4 grams/day or placebo. IPE reduced the primary (CV death, myocardial infarction [MI], stroke, coronary revascularization, hospitalization for unstable angina) and key secondary (CV death, MI, stroke) endpoints 25% and 26%, respectively (each p<0.0001), and individual components including stroke (28%), MI (31%), cardiac arrest (48%), and sudden cardiac death (31%) (all p≤0.01). With IPE, bleeding was greater (11.8% vs 9.9%; p=0.006), serious bleeding trended higher (2.7% vs 2.1%; p=0.06), and atrial fibrillation/flutter (AF/F) hospitalization endpoints increased (3.1% vs 2.1%; p=0.004).

Purpose

To evaluate the effects of IPE on the risk of CV events and safety measures in patients by either history of AF/F or in-study occurrence of positively adjudicated AF/F hospitalization.

Methods

Conduct post hoc efficacy and safety subgroup analyses of patients with or without either baseline history of AF/F or in-study adjudicated AF/F hospitalization, including hospitalization for ≥24 hours; AF/F not meeting endpoint criteria were reported as adverse events.

Results

Patients with (n=751; 9.2%) AF/F history at baseline (vs without; n=7428; 90.8%) (Figure 1), or those with (n=211; 2.6%) positively adjudicated in-study AF/F hospitalization endpoints (vs without; n=7968; 97.4%) (Figure 2), had higher event rates of primary, key secondary, and fatal or nonfatal stroke endpoints, but relative risk reductions with IPE were not significantly different (all interaction p-values [pint]=ns). Similar reductions were observed with IPE across the prespecified endpoint testing hierarchy in patients with or without AF/F history or in-study hospitalization endpoints. Patients with baseline AF/F history had similar relative risk for in-study occurrence of AF/F hospitalization with IPE versus placebo (pint=0.21) but had greater absolute risk (12.5% vs 6.3%, IPE vs placebo) vs patients without baseline AF/F history (2.2% vs 1.6%, IPE vs placebo); i.e., recurrent AF/F in those with a prior history of AF/F was more prevalent than de novo AF/F. Serious bleeding trended higher regardless of AF/F history or in-study AF/F hospitalization endpoints (all pint=ns); absolute risk of serious bleeding was greater in patients with AF/F history at baseline (7.3% vs 6.0%) vs those without a baseline history of AF/F (2.3% vs 1.7%), and serious bleeding also trended higher in patients with in-study AF/F hospitalization (8.7% vs 6.0%) vs without (2.5% vs 2.0%) [all IPE vs placebo].

Conclusion

REDUCE-IT patients with AF/F history or in-study AF/F hospitalization endpoints had greater CV risk, but similar relative risk reduction in primary, key secondary, and fatal or nonfatal stroke endpoints with IPE.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Amarin Pharma, Inc.

Influence of cardiovascular drugs on the efficacy and safety of dapagliflozin in patients with type 2 diabetes mellitus in the DECLARE-TIMI 58 trial

Background

In DECLARE-TIMI 58, the sodium glucose co-transporter 2 inhibitor (SGLT2i) dapagliflozin reduced the risk of the composite of cardiovascular (CV) death or hospitalization for heart failure (HHF) in a broad range of patients with type 2 diabetes mellitus (T2DM). SGLT2i are known to have diuretic and anti-hypertensive effects. However, whether concomitant CV drugs influence the efficacy and safety of dapagliflozin in these populations is less well known.

Purpose

We examined whether dapagliflozin consistently reduced the risk of CV outcomes and whether the safety of dapagliflozin was similar with or without the concurrent use of various CV drugs.

Methods

DECLARE–TIMI 58 was a randomized trial of dapagliflozin versus placebo in patients with T2DM and either atherosclerotic cardiovascular disease (ASCVD) or multiple risk factors for CV disease followed for a median of 4.2 years. We stratified patients by the use of CV drugs at baseline commonly used for heart failure: angiotensin-converting-enzyme inhibitors or angiotensin-receptor blockers (ACEi/ARB), beta-blockers, diuretics, and mineralocorticoid receptor antagonists (MRA). Efficacy outcomes of interest were the composite of CV death/HHF and HHF alone. We used the Cox proportional-hazard model for these analyses.

Results

Of 17,160 patients, 13,950 (81%) used ACEi/ARB, 9,030 (53%) used beta-blockers, 6,967 (41%) used diuretics, and 762 (4%) used MRA at baseline. All were balanced by randomized treatment groups. Patients using CV drugs at baseline had a greater prevalence of atherosclerotic risk factors and established CV disease than those without. Dapagliflozin consistently reduced the risk of CV death/HHF regardless of the use of CV medications (Figure). For HHF alone, similar results were seen with no significant interactions for any of the classes. There were no significant treatment interactions by the concomitant use of any of CV drugs for adverse events including symptoms of volume depletion or acute kidney injury.

Conclusions

In this analysis from the DECLARE–TIMI 58 trial, dapagliflozin consistently reduced the risk of CV death/HHF and HHF alone irrespective of the concurrent use of various CV drugs without any treatment interaction for key safety events.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The DECLARE–TIMI 58 trial was supported by AstraZeneca.

STARTRAC analyses of scRNAseq data from tumor models reveal T cell dynamics and therapeutic targets

Single-cell RNA sequencing is a powerful tool to examine cellular heterogeneity, novel markers and target genes, and therapeutic mechanisms in human cancers and animal models. Here, we analyzed single-cell RNA sequencing data of T cells obtained from multiple mouse tumor models by PCA-based subclustering coupled with TCR tracking using the STARTRAC algorithm. This approach revealed various differentiated T cell subsets and activation states, and a correspondence of T cell subsets between human and mouse tumors. STARTRAC analyses demonstrated peripheral T cell subsets that were developmentally connected with tumor-infiltrating CD8⁺ cells, CD4⁺ Th1 cells, and T reg cells. In addition, large amounts of paired TCRα/β sequences enabled us to identify a specific enrichment of paired public TCR clones in tumor. Finally, we identified CCR8 as a tumor-associated T reg cell marker that could preferentially deplete tumor-associated T reg cells. We showed that CCR8-depleting antibody treatment provided therapeutic benefit in CT26 tumors and synergized with anti–PD-1 treatment in MC38 and B16F10 tumor models.

Systematic comparison of high-throughput single-cell RNA-seq methods for immune cell profiling

BACKGROUND

Elucidation of immune populations with single-cell RNA-seq has greatly benefited the field of immunology by deepening the characterization of immune heterogeneity and leading to the discovery of new subtypes. However, single-cell methods inherently suffer from limitations in the recovery of complete transcriptomes due to the prevalence of cellular and transcriptional dropout events. This issue is often compounded by limited sample availability and limited prior knowledge of heterogeneity, which can confound data interpretation.

RESULTS

Here, we systematically benchmarked seven high-throughput single-cell RNA-seq methods. We prepared 21 libraries under identical conditions of a defined mixture of two human and two murine lymphocyte cell lines, simulating heterogeneity across immune-cell types and cell sizes. We evaluated methods by their cell recovery rate, library efficiency, sensitivity, and ability to recover expression signatures for each cell type. We observed higher mRNA detection sensitivity with the 10x Genomics 5' v1 and 3' v3 methods. We demonstrate that these methods have fewer dropout events, which facilitates the identification of differentially-expressed genes and improves the concordance of single-cell profiles to immune bulk RNA-seq signatures.

CONCLUSION

Overall, our characterization of immune cell mixtures provides useful metrics, which can guide selection of a high-throughput single-cell RNA-seq method for profiling more complex immune-cell heterogeneity usually found in vivo.

REDUCE-IT: outcomes by baseline statin type

Background

REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial) randomized 8,179 statin-treated patients with elevated triglycerides and increased cardiovascular (CV) risk to either icosapent ethyl (IPE), a pure, stable prescription form of eicosapentaenoic acid, 4g/day or placebo. IPE significantly reduced time to first occurrence of the primary composite endpoint of major adverse CV events (CV death, nonfatal myocardial infarction [MI], nonfatal stroke, coronary revascularization, or hospitalization for unstable angina) (HR 0.75, CI 0.68–0.83) and key secondary endpoint events (composite of CV death, nonfatal MI, or nonfatal stroke) (HR 0.74, CI 0.65–0.83) versus placebo (all p<0.0001). A modest reduction in placebo-corrected LDL-C was observed (−6.6%; p<0.0001). The mechanisms for the CV benefit of icosapent ethyl are not fully understood.

Purpose

Explore the impact of statin type and lipophilic/lipophobic category on outcomes, and on LDL-C, to further consider the possible relevance of LDL-C pathways to the observed CV benefit of icosapent ethyl.

Methods

Primary and key secondary endpoint analyses and LDL-C changes from baseline were explored by individual statin type (atorvastatin, simvastatin, rosuvastatin, or pravastatin) at baseline, and then by categorizing these statins into lipophilic (i.e., hydrophobic: atorvastatin, simvastatin) and lipophobic (i.e., hydrophilic: rosuvastatin, pravastatin) statin groups; 96.1% of patients fell within these individual statin groups.

Results

CV outcomes were similar across statin types (interaction p=0.61) and lipophilic/lipophobic categories (interaction p=0.51) (Figure). Statin type and category had a similar lack of meaningful impact on the modest placebo-corrected median LDL-C changes from baseline to one year, which ranged from −5.8 to −8.4% (all p≤0.0003).

Conclusion

No meaningful treatment differences in the primary or key secondary endpoints across statin type or lipophilic/lipophobic category were observed. A similar lack of treatment difference was observed in LDL-C changes from baseline to one year. Therefore, the LDL-C changes and CV risk reduction in REDUCE-IT appear independent of the type of concomitant statin therapy. These data provide clinicians with additional insight regarding concomitant statin therapy considerations when prescribing icosapent ethyl and suggest there are important mechanisms of action for the substantial CV risk reduction observed with icosapent ethyl that are distinct from the LDL receptor pathway.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The study was funded by Amarin Pharma, Inc.

Single-Cell Analyses Inform Mechanisms of Myeloid-Targeted Therapies in Colon Cancer

Single-cell RNA sequencing (scRNA-seq) is a powerful tool for defining cellular diversity in tumors, but its application toward dissecting mechanisms underlying immune-modulating therapies is scarce. We performed scRNA-seq analyses on immune and stromal populations from colorectal cancer patients, identifying specific macrophage and conventional dendritic cell (cDC) subsets as key mediators of cellular cross-talk in the tumor microenvironment. Defining comparable myeloid populations in mouse tumors enabled characterization of their response to myeloid-targeted immunotherapy. Treatment with anti-CSF1R preferentially depleted macrophages with an inflammatory signature but spared macrophage populations that in mouse and human expresses pro-angiogenic/tumorigenic genes. Treatment with a CD40 agonist antibody preferentially activated a cDC population and increased Bhlhe40⁺ Th1-like cells and CD8⁺ memory T cells. Our comprehensive analysis of key myeloid subsets in human and mouse identifies critical cellular interactions regulating tumor immunity and defines mechanisms underlying myeloid-targeted immunotherapies currently undergoing clinical testing.

REDUCE-IT: accumulation of data across prespecified interim analyses to final results

Background

REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial), an event-driven trial, randomized 8,179 statin-treated patients with elevated triglycerides (TGs) and increased cardiovascular (CV) risk to icosapent ethyl (IPE); pure, stable prescription eicosapentaenoic acid, 4g/day or placebo. 1,612 primary endpoint events (CV death, nonfatal myocardial infarction [MI], nonfatal stroke, coronary revascularization, or hospitalization for unstable angina) projected 90% power to detect 15% relative risk reduction (5% 2-sided alpha). The key secondary composite endpoint was CV death, nonfatal MI, or nonfatal stroke. An independent data and safety monitoring committee (DMC) performed prespecified interim analyses (IAs) at ∼60% (IA1 31 May 2016 data cutoff; 2.9 y median primary endpoint follow-up) and ∼80% (IA2 01 May 2017; 3.7 y) of events; final analysis included 1,606 events (06 Sep 2018; 4.9 y median study follow-up).

Purpose

Explore REDUCE-IT efficacy and safety across prespecified IAs for insight into progression of robustness and consistency of conclusions.

Methods

The interim statistical analysis plan guided study continuation decisions by a prespecified decision-making process, including assessment of safety, treatment arm performance, primary composite endpoint formal analyses, and informal robustness analyses, with no futility or efficacy stopping requirements. Prior to DMC IA study continuation decisions, the need for a mature dataset to support the robustness of final efficacy and safety findings was discussed. Sponsor, Steering Committee, and Clinical Endpoint Committee were blinded throughout.

Results

Primary and key secondary endpoints achieved statistical significance at IA1 and IA2 that persisted at final analyses (p-value below final adjusted 2-sided alpha of 0.0437); hazard ratios also remained consistent and similar robustness was observed across individual endpoint components; clarity of findings across endpoints and subgroups improved with more events. Stopping for overwhelming efficacy was discussed at each IA; prior to IA study continuation recommendations, the DMC considered historical examples of failed CV outcome studies for TG-lowering and mixed omega-3 therapies, reflected on the potential for overestimating final demonstrated benefit using incomplete data, and weighed societal impacts of fuller datasets relative to patient therapy access.

Conclusions

Consistent, potent efficacy emerged early and persisted across the two prespecified interim and final analyses. The mature dataset demonstrated highly statistically significant reductions in the primary (25%; p=0.00000001) and key secondary (26%; p=0.0000006) endpoints and allowed robust analyses to support overall efficacy and safety conclusions. Allowing the REDUCE-IT dataset to fully mature provided clinicians with robust, consistent, and reliable data upon which to base clinical decisions for IPE in CV risk reduction.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The study was funded by Amarin Pharma, Inc.

REDUCE-IT: total ischemic events reduced across the full range of baseline LDL cholesterol and other key subgroups

Background

REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial), a study of 8,179 randomized statin-treated patients with elevated triglycerides (TG) and increased cardiovascular (CV) risk followed for a median of 4.9 years, demonstrated robust results. Icosapent ethyl (IPE), a pure and stable prescription form of eicosapentaenoic acid, 4g/day reduced both time-to-first and total primary endpoint ischemic events (CV death, nonfatal myocardial infarction [MI], nonfatal stroke, coronary revascularization, or hospitalization for unstable angina) by 25% (HR 0.75; 95% CI 0.68–0.83; p<0.0001) and 30% (rate ratio 0.70; 95% CI 0.62–0.78; p<0.0001), respectively. Similar substantial reductions in first and total key secondary endpoint ischemic events (composite of CV death, nonfatal MI, or nonfatal stroke) were also observed. Demographic and baseline disease characteristics were generally balanced across treatment groups. Time-to-first event analyses showed robust and generally consistent benefit across subgroups. Previous total event analyses by baseline TG demonstrated large, consistent, statistically significant reductions across tertiles, suggesting the CV benefit of IPE is tied primarily to non-TG factors.

Purpose

Further explore the extent to which IPE reduced total primary and key secondary events across prespecified baseline demographic, disease, treatment, and lipid/lipoprotein/inflammatory biomarker subgroups.

Methods

Total events across subgroups were assessed with the prespecified negative binomial regression method. Main outcomes were total (first and subsequent) primary and key secondary composite endpoint events.

Results

Median baseline LDL-C levels in ascending tertiles were 58, 76, and 96 mg/dL; there were large, significant relative reductions in total primary endpoint events with IPE across tertiles (35%, 28%, and 27%, respectively; interaction p=0.62), with parallel substantial absolute risk reductions. Similar, significant relative reductions of 33%, 28%, and 24% in total key secondary endpoint events were observed, along with substantial absolute risk reductions. Total events analyses of prespecified subgroups also demonstrated robust and generally consistent findings for the primary and key secondary composite endpoints.

Conclusion

REDUCE-IT demonstrated substantial reductions in first and total primary and key secondary endpoint ischemic events, with robust and generally consistent results across baseline TG and LDL-C levels, as well as other prespecified baseline biomarker, demographic, disease, and treatment subgroups. These analyses provide useful insights for clinicians considering the range of patients who may benefit from IPE therapy and suggest that mechanisms beyond the lipid/lipoprotein/inflammatory pathways tested, including mechanisms beyond the LDL receptor pathways, may contribute to the observed substantial reductions in total ischemic burden with IPE therapy.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The study was funded by Amarin Pharma, Inc.

Toll-like Receptor (TLR)-induced Rasgef1b expression in macrophages is regulated by NF-κB through its proximal promoter

Ras Guanine Exchange Factor (RasGEF) domain family member 1b is encoded by a Toll-like receptor (TLR)-inducible gene expressed in macrophages, but transcriptional mechanisms that govern its expression are still unknown. Here, we have functionally characterized the 5' flanking Rasgef1b sequence and analyzed its transcriptional activation. We have identified that the inflammation-responsive promoter is contained within a short sequence (-183 to +119) surrounding the transcriptional start site. The promoter sequence is evolutionarily conserved and harbors a cluster of five NF-κB binding sites. Luciferase reporter gene assay showed that the promoter is responsive to TLR activation and RelA or cRel, but not RelB, transcription factors. Besides, site-directed mutagenesis showed that the κB binding sites are required for maximal promoter activation induced by LPS. Analysis by Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) revealed that the promoter is located in an accessible chromatin region. More important, Chromatin Immunoprecipitation sequencing (ChIP-seq) showed that RelA is recruited to the promoter region upon LPS stimulation of bone marrow-derived macrophages. Finally, studies with Rela-deficient macrophages or pharmacological inhibition by Bay11-7082 showed that NF-κB is required for optimal Rasgef1b expression induced by TLR agonists. Our data provide evidence of the regulatory mechanism mediated by NF-κB that facilitates Rasgef1b expression after TLR activation in macrophages.

Chemical chaperones reverse early suppression of regulatory circuits during unfolded protein response in B cells from common variable immunodeficiency patients

B cells orchestrate pro-survival and pro-apoptotic inputs during unfolded protein response (UPR) to translate, fold, sort, secrete and recycle immunoglobulins. In common variable immunodeficiency (CVID) patients, activated B cells are predisposed to an overload of abnormally processed, misfolded immunoglobulins. Using highly accurate transcript measurements, we show that expression of UPR genes and immunoglobulin chains differs qualitatively and quantitatively during the first 4 h of chemically induced UPR in B cells from CVID patients and a healthy subject. We tested thapsigargin or tunicamycin as stressors and 4-phenylbutyrate, dimethyl sulfoxide and tauroursodeoxycholic acid as chemical chaperones. We found an early and robust decrease of the UPR upon endoplasmic reticulum (ER) stress in CVID patient cells compared to the healthy control consistent with the disease phenotype. The chemical chaperones increased the UPR in the CVID patient cells in response to the stressors, suggesting that misfolded immunoglobulins were stabilized. We suggest that the AMP-dependent transcription factor alpha branch of the UPR is disturbed in CVID patients, underlying the observed expression behavior.

410Heart failure risk stratification and efficacy of dapagliflozin in patients with type 2 diabetes mellitus

Background

Patients with type 2 diabetes mellitus (T2DM) are at increased risk of developing heart failure (HF). Treatment with sodium-glucose cotransporter-2 (SGLT2) inhibitors reduces the risk of hospitalization for HF (HHF) in patients with T2DM.

Purpose

To develop and validate a practical, multivariable clinical risk score for HHF in patients with T2DM and assess whether this score can identify high-risk patients with T2DM who have the greatest reduction in risk for HHF with an SGLT2 inhibitor.

Methods

We developed a clinical risk score for centrally-adjudicated HHF using independent clinical risk indicators of HHF in 8212 patients with T2DM in the placebo arm of SAVOR-TIMI 53. Candidate variables were assessed using multivariable Cox regression and independent clinical risk indicators achieving statistical significance of p<0.001 were included in the risk score and given weights proportional to the regression coefficients. We externally validated the score in 8578 patients with T2DM in the placebo arm of DECLARE-TIMI 58. Discrimination was assessed using Harrell's c-index. The relative and absolute risk reductions in HHF with the SGLT2 inhibitor dapagliflozin were assessed by baseline HHF risk.

Results

The 5 independent clinical risk indicators were prior heart failure, atrial fibrillation, coronary artery disease, estimated glomerular filtration rate (eGFR), and urine albumin/creatinine ratio (UACR) (Figure, left). A simple integer-based scheme using these predictors identified a strong >16-fold gradient of HHF risk (p-trend <0.001) in both the derivation and validation cohorts, with c-indices of 0.81 and 0.78, respectively. Whereas relative risk reductions were similar across the risk score (25–34%), absolute risk reductions were greater in those at higher baseline risk (interaction p-value for absolute risk reduction <0.01), with high-risk (2 points) and very high-risk patients (≥3 points) having 1.5% and 2.7% absolute risk reductions in HHF at 4 years with dapagliflozin, translating into NNTs of only 65 and 36, respectively (Figure, right).

Conclusion(s)

Risk stratification using a novel clinical risk score for HHF in patients with T2DM identifies patients at higher risk for HHF who derive greater benefit from treatment with the SGLT2 inhibitor dapagliflozin.

Acknowledgement/Funding

SAVOR-TIMI 53 and DECLARE-TIMI 58 were sponsored by AstraZeneca.

Regulation of the NF-κB-Mediated Transcription of Inflammatory Genes

The NF-κB family of transcription factors plays a central role in the inducible expression of inflammatory genes during the immune response, and the proper regulation of these genes is a critical factor in the maintenance of immune homeostasis. The chromatin environment at stimulus-responsive NF-κB sites is a major determinant in transcription factor binding, and dynamic alteration of the chromatin state to facilitate transcription factor binding is a key regulatory mechanism. NF-κB is in turn able to influence the chromatin state through a variety of mechanisms, including the recruitment of chromatin modifying co-activator complexes such as p300, the competitive eviction of negative chromatin modifications, and the recruitment of components of the general transcriptional machinery. Frequently, the selective interaction with these co-activators is dependent on specific post-translational modification of NF-κB subunits. Finally, the mechanisms of inducible NF-κB activity in different immune cell types seem to be largely conserved. The diversity of cell-specific NF-κB-mediated transcriptional programs is established at the chromatin level during cell differentiation by lineage-defining transcription factors. These factors generate and maintain a cell-specific chromatin landscape that is accessible to NF-κB, thus restricting the inducible transcriptional response to a cell-appropriate output.

Investigating the Role of Plasma Glucose Concentration as a Phenotypic Marker for CYP2C9 Genetic Variants, in the Diabetic Population of Gujarat

The present study was aimed to investigate the role of plasma glucose concentration as a phenotypic marker and to study the frequency distribution of CYP2C9 genetic variants in Gujarat state diabetic population. One hundred and nine unrelated diabetes mellitus patients treated with sulfonylureas were genotyped for CYP2C9*2 and CYP2C9*3 alleles. Their pre- and posttreatment postprandial blood glucose levels were recorded and mean glucose drop per milligram of drug values were calculated and further used as an index for phenotypic correlation. The frequencies of CYP2C9*1, CYP2C9*2 and CYP2C9*3 alleles in the Gujarat state diabetic population were 0.84, 0.07 and 0.09, respectively. The distribution of CYP2C9*1/*1, CYP2C9*1/*2, CYP2C9*1/*3, CYP2C9*2/*2, CYP2C9*2/*3 and CYP2C9*3/*3 genotypes were 0.73, 0.08, 0.13, 0.0, 0.06 and 0.0, respectively. Patients with CYP2C9*1/*2 genotype did not show any significant difference in the mean glucose drop per milligram of drug values when compared with wild-type patients in glipizide-treatment group. Patients with CYP2C9*1/*3 genotype showed greater mean glucose drop per milligram of drug values than patients with CYP2C9*1/*1 wild-type genotype for both glipizide and glimepiride while patients with CYP2C9*2/*3 genotype showed greater drop than patients with CYP2C9*1/*1 genotype only in the glipizide-treatment group. The presence of CYP2C9*3 allele significantly affected plasma glucose drop per milligram of drug values in patients taking glipizide and glimepiride, while effects of CYP2C9*2 allele were insignificant. Further studies are needed to confirm the effects of CYP2C9*2 allele on plasma glucose drop per milligram of drug values. However, plasma glucose concentration is a complex physiological marker that cannot be used to establish perfect genotype-phenotype correlation. Hence studies exploring robust phenotypic markers must be initiated.

Thermal motions of the E. coli glucose-galactose binding protein studied using well-sampled, semi-atomistic simulations

The E. coli glucose-galactose chemosensory receptor is a 309 residue, 32 kDa protein consisting of two distinct structural domains. We used two computational methods to examine the protein's thermal fluctuations, including both the large-scale interdomain movements that contribute to the receptor's mechanism of action, as well as smaller-scale motions. We primarily employ extremely fast, "semi-atomistic" Library-Based Monte Carlo (LBMC) simulations, which include all backbone atoms but "implicit" side chains. Our results were compared with previous experiments and all-atom molecular dynamics (MD) simulation. Both LBMC and MD simulations were performed using both the apo and glucose-bound form of the protein, with LBMC exhibiting significantly larger fluctuations. The LBMC simulations are in general agreement with the disulfide trapping experiments of Careaga & Falke (J. Mol. Biol., 1992, Vol. 226, 1219-35), which indicate that distant residues in the crystal structure (i.e. beta carbons separated by 10 to 20 angstroms) form spontaneous transient contacts in solution. Our simulations illustrate several possible "mechanisms" (configurational pathways) for these fluctuations. We also observe several discrepancies between our calculations and experimental rate constants. Nevertheless, we believe that our semi-atomistic approach could be used to study fluctuations in other proteins, perhaps for ensemble docking or other analyses of protein flexibility in virtual screening studies.

Furthering pharmacological and physiological assessment of the glutamatergic receptors at the Drosophila neuromuscular junction

Drosophila melanogaster larval neuromuscular junctions (NMJs) serve as a model for synaptic physiology. The molecular sequences of the postsynaptic glutamate receptors have been described; however, the pharmacological profile has not been fully elucidated. The postsynaptic molecular sequence suggests a novel glutamate receptor subtype. Kainate does not depolarize the muscle, but dampens evoked EPSP amplitudes. Quantal responses show a decreased amplitude and area under the voltage curve indicative of reduced postsynaptic receptor sensitivity to glutamate transmission. ATPA, a kainate receptor agonist, did not mimic kainate's action. The metabotropic glutamate receptor agonist t-ACPD had no effect. Domoic acid, a kainate/AMPA receptor agonist, blocks the postsynaptic receptors without depolarizing the muscle. However, SYM 2081, a kainate receptor agonist, did depolarize the muscle and reduce the EPSP amplitude at 1 mM but not at 0.1 mM. This supports the notion that these are generally a quisqualate subtype receptors with some oddities in the pharmacological profile. The results suggest a direct postsynaptic action of kainate due to partial antagonist action on the quisqualate receptors. There does not appear to be presynaptic auto-regulation via a kainate receptor subtype or a metabotropic auto-receptor. This study aids in furthering the pharmokinetic profiling and specificity of the receptor subtypes.

Vocal signals in a tropical Avian species, the redvented bulbul Pycnonotus cafer: their characteristics and importance

Acoustic signals play an important role in the lives of birds. Almost all avian species produce vocal signals in a variety of contexts either in the form of calls or songs or both. In the present study different types of vocal signals of the tropical avian species Pycnonotus cafer were characterized on the basis of their physical characteristics and context of production. This species used six types of vocal signals: contact signals, roosting signals, alarm signals, twittering signals, distress signals and begging signals. Two types of alarm signals are produced based on predation pressure. These signals are dissimilar in all physical characteristics except for dominant frequency. Although alarm signal type I and roosting signals are phonetically similar, they have completely different sonogram characteristics.